The overriding lesson of the Lebanon truck-bomb tragedy is its reminder of the limitations of military power against irrational forces, or in situations where only limited power can be applied.
It was almost exactly four years ago - Nov. 4, 1979 - that Americans and the rest of the world were stunned by the news that ''Muslim students'' had taken over the US Embassy in Iran. There followed, after the first days of confusion over the identity and motives of the assailants, more than a year of agonized waiting for the hostages' release. The heart-rending episode ended, with a bitter twist, the day Ronald Reagan took office and Jimmy Carter left - the promiser of renewed American assertiveness abroad replacing a man who had sought Middle East peace only to be ousted at home as a symbol of US impotence.
The Iranian reminder is useful, because it is both more recent than the Vietnam involvement, and more limited than that involvement eventually became. As with Iran then, the United States cannot now react with anger, as the initial White House response appeared to suggest. Retribution is obviously immaterial, when the identity and motive of the terrorists who attacked the US Marine and French paratrooper quarters remain in doubt.
Now what should the Reagan administration do?
First, the White House should not allow itself to become captive of the Lebanon atrocity the way Jimmy Carter made himself and his reelection campaign hostage to the Iranian drama. Remember the lightless Christmas tree, the Rose Garden campaign strategy of claiming the President was preoccupied with the hostages' plight? President Reagan must keep the larger picture of his national and world responsibilities in view and not feel pressed to some premature or needlessly bold action. Just as Americans extended to Mr. Carter an extraordinary level of support throughout his ordeal, so can Mr. Reagan count on the good sense of Americans today until he can work out a rational response.
Second, Mr. Reagan should acknowledge the role of Congress hereafter on the Lebanese front. Given the severity of US Marine losses, it would appear unseemly to haggle further with Congress over authority for Marine deployment under the War Powers Act. The earlier deal with Congress - 18 months of deployment in exchange for a guarded and debatable acknowledgment of congressional review and authority - is off.
Third, on the military side, the Sunday explosions exposed the vulnerability of the Marine compound that should have been obvious from the outset. This fact should be acknowledged. Congress will investigate it anyway, so why justify a tactical risk that misfired? Two opposing ideas for the Marines - removal to offshore, ship-based stations, or permitting aggressive search patrols around Lebanon - have been proposed. Neither offshore withdrawal nor escalation appears adequate. They would produce either an ineffective ''peacekeeping'' presence in the water or a more vulnerable multinational force on the ground. Congress now has too many authoritative analysts of its own to allow the administration room for anything but candor. Congress will demand to know how the military could have permitted the second terrorist bomb attack in the area in six months.
Fourth, on the diplomatic side, the administration should seek a multinational approach to Lebanon's conflict. Sending the Marines never really constituted a Lebanon policy. The US Marines got into Lebanon as guarantors, along with British, French, and Italian troops, of Lebanese peace after the Israeli pullout. The idea was to give President Gemayel time enough to build a military of his own and forge a coalition among Lebanon's bitter factions. A bloodbath of Christian Lebanese, who control the government, was feared at the hands of Muslim factions. A sudden pullout could still result in tragic civilian losses, and Americans would feel the worse for that. Still, a comprehensive effort to stabilize Lebanon is needed. Israel's presence in the south, as well as Syria's, must be taken into account. How to guarantee Israel's interests, how to coordinate Muslim pressure on a Syria dangerously toying with Soviet backup, must be worked out. Barring a cohesive effort of friendly nations to strengthen the Beirut government, the US Marines should be pulled out. The President should be given a reasonable time to try a new Lebanon approach, possibly until his reelection decision announcement, now apparently postponed until January.
Finally, and inevitably, the politics of the Marine tragedy's aftermath: If ever there were a time for emphasizing the bipartisan fundamentals of foreign policy, this is it. Mr. Reagan had never really sold the public on his Marine mission in the first place. More than two-thirds of the public thinks he failed to explain his case. A majority disapproved of the mission. That is a weak political position for Mr. Reagan to stand on. Democratic presidential candidates would be wise to emphasize solutions for the region rather than take partisan advantage of Mr. Reagan's vulnerability at the moment. Just as an ''October surprise'' hostage release before the 1980 election was warned of by Reagan's political strategists, so a workable Lebanon pact by Reagan could undercut Democratic opportunism. Nonetheless, Democratic candidates will have to argue clearly and forcefully their views on the Middle East if they are to represent their candidacies seriously.
It is hard to overstate the stakes in the Lebanese situation. It is a test of the Reagan presidency. Other recent Presidents - Johnson and Vietnam, Carter and Iran - have had their presidential careers, noteworthy on other counts, cut short by extraneous foreign adventures.
The limitations of decency on a mighty democracy - the need to avoid a scorched-earth response to provocation - can at times make it appear weak.
Lebanon is not a test of American might. It is a test of American wisdom, diplomatic skill, and patience. Peace-loving people everywhere want Mr. Reagan to find either the right justification for continuing the Marine presence in Lebanon, or to take them out.